Hybrids between mouse hepatoma cells and human leukocytes have been shown to secrete human serum albumin. I plan to use somatic cell hybrids between murine hepatoma lines and human diploid ones to define the conditions under which human genes can be activated to produce hepatic proteins. The feasibility of using activated amniotic fluid cells for antenatal diagnosis will be examined. The linkage relationships of human hepatic loci will be determined by standard procedures of gene mapping. The phenomenon of activation will be studied to determine the kind of genetic components involved in expression of the albumin gene. Finally, embryonic cells at various developmental stages will be tested for their capacity to express organ specific functions following hybridization with differentiated hepatoma cells.